Gas-cluster ion beams (GCIB's) are used for etching, cleaning, smoothing, and forming thin films. For purposes of this discussion, gas clusters are nano-sized aggregates of materials that are gaseous under conditions of standard temperature and pressure. Such gas clusters may consist of aggregates including a few to several thousand molecules, or more, that are loosely bound together. The gas clusters can be ionized by electron bombardment, which permits the gas clusters to be formed into directed beams of controllable energy. Although GCIB processing of workpieces is performed using a wide variety of gas-cluster source gases, many of which are inert gases, many semiconductor processing applications use reactive source gases, sometimes in combination or mixture with inert or noble gases, to form the GCIB.
Measurement of thin films may be performed using measurement techniques utilizing reflection scattering, diffraction, spectroscopy, and/or polarization detection using a beam of light, x-rays, or electrons. Features on films or workpieces may be measured using optical digital profilometry, which is a non-destructive metrology technology that utilizes optical instruments based on spectroscopic ellipsometry or reflectometry to precisely measure critical dimensions (CDs), sidewall angles, and multiple layer film thicknesses. These measurements can be made on both two-dimensional line/space structures, as well as three-dimensional hole or island structures. The process is executed in-line, which eliminates the need to destructively process the wafer to perform the analyses.